1. Field of the Invention
Gas burners that incorporate two and three flame rings are known in the field of the art. Generally, a flame ring that is located in the center of the gas burner is designated as a warming burner. The outer flame ring and middle flame ring, if any, are designated as the main burner.
It is common for the main burner to generate a heat output greater than 10,000 Btu/hr (British thermal units per hour). The heat output generated by the warming burner, at its lowest setting, can be reduced to approximately 600 Btu/hr, without extinguishing the flame. The diameter of the flame rings determine the heat output of the burner. Since the warming burner generates a lower Btu/hr output than the main burner, the warming burner has a smaller diameter than the main burner. The warming burner is approximately 1/2 inch in diameter, while the main burner is approximately 4 inches in diameter.
Maximum burner output is achieved when the main burner and the warming burner are both operating at their maximum outputs. After the main burner is shut off, only the warming burner is operating, and it can be regulated by adjusting the burner valve. The purpose of the warming burner is not only to keep cooked foods warm, but also can be used to melt butter or chocolate, without browning the butter or burning the chocolate.
The disadvantage of a singular warming burner, which is located in the center of the burner assembly, is that the warming burner has a very small diameter. The heat of the warming burner is then generated over a very small area under a pot or pan, which results in uneven cooking at the lower operating temperatures.
Burners caps for this type of burner are generally designed in two pieces. Each of the separate pieces are shaped as thin concentric rings. The main burner cap has gas outlet slots or holes arranged on the sides of the burner cap, forming a ring of flame when a flammable gas is ignited. A second burner cap, which is smaller in diameter than the main burner cap (called a warming burner), also has gas outlet slots or holes arranged on the sides of the burner cap and also will form a ring of flame when a flammable gas is ignited. The caps of both the main burner and the warming burner are loosely positioned, concentrically to each other, on the top of the burner head. The disadvantage of this design is that the burner cap of the warming burner is so small in diameter that it is easily lost.
An additional disadvantage of burners designed in this manner is that the gas jets that were previously installed in the gas/air mixing tubes (called air mixers) are not accessible from the top of the appliance. In order to adjust the appliance to accommodate a different type of flammable gas, the top of the burner assembly must be removed from the appliance. The top of the appliance must also be removed in order to gain access to the gas jets.
Ignition electrodes installed in these burner assemblies have a similar drawback. The ignition electrodes are generally installed from the bottom side of the burner head, or next to the burner from the bottom of the appliance top. These drawbacks sometimes cause service personnel even greater problems, and results in higher costs for the consumer. After prolonged operation of the gas appliance, the screws, clips and other fasteners are quite difficult to loosen.
2. Description of the Prior Art
The use of a multi-ring gas burner is known in the prior art.
U.S. Pat. No. 5,295,476 describes a burner plate that has a series of concentric rings, the concentric rings each being perforated to match the arrangement of concentric chambers to provide concentric gas burning rings. Control valves regulate the flow of gas to the burner plate perforation where heat is required. This unit operates with the use of an electrical thermocouple to maintain a predetermined heat level. As the control valve is turned, a specific number of rings are ignited to provide the required heat. This invention uses a very complex valve assembly to provide the gas requirements to the burner hob.
U.S. Pat. No. 1,716,329 describes a combination gas and electric stove. The gas portion of the stove provides gas from an inner chamber to a series of perforations in the burner top. The difference between the described patent and the present invention is that the gas output to all the perforations is the same, where the present invention has a varied heat capacity over the burner cap.
U.S. Pat. No. 5,397,135 describes a commercial gas burner structure. A plurality of upright portions are mounted on a plate portion. A chamber is located below the plate portion, where passageways extend from the chamber and pass outwardly through the upright portions. The described patent has upright flame, and all the upright portions provide flame, where the present invention only has specific flame rings in operation.
U.S. Pat. No. 4,313,416 describes a heating element for a wok shaped cooking utensil. A spiraling gas tube describes a series of concentric rings, where the concentric rings have perforations that provide the requisite flame when ignited. This s patent describes an invention that provides for all the perforations to provide flame at the same time.
U.S. Pat. No. 3.843,313 describes a multi-cavity radiant burner. A series of annular cavities regulated by a valve allows a liquid flammable fuel such as gas to enter into each of the cavities where they are ignited. The three cavities are supplied progressively. First to the inner, then to the middle, and finally to the outer cavity, where the inner cavity will provide the least amount of radiant heat, and the generated heat gets progressively greater with ignition of each successive ring. This patent requires that the burner ring provide the combustion surface. By opening the valve to initiate ignition of the middle burner cavity, the inner cavity is provided with its maximum radiant capability, thereby having greater heat capacity at all levels, but not capable of good low temperature cooking.